Transcript ppt-sgcp-2000

SGCP Simple Gateway Control
Protocol
Christian Huitema
[email protected]
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Internet Systems
May 1998
Page 1
State of the art, trunking GW
SS7 relay => non standard, delays
H.323 => transparency, delays
TGW => real time, software ?
STP
SS7 GW
SS7 GW
IP Network
CO
Internet Systems
relay ?
TGW
TGW
<- H.323 ->
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STP
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C
O
SGCP: trunking gateway
SS7
STP
SGCP endpoint
SS7 trunk group
Call Agent
TGW-1
TGW-2
CO
TGW-3
Phys-R3W/15 @ tgw-1.example.net
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Page 3
SGCP architecture (TGW)
The call agent implements the SS7/ISUP
standards. It uses SGCP to “remote control”
the gateways.
SS7/ISUP
STP
Call
agent
SS7/ISUP
STP
SGCP/UDP
IP Network
CO
TGW
TGW
RTP
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May 1998
Page 4
CO
SGCP: connection set-up
SDP: Session
Description
Protocol (RFC 2327)
Call
agent
1- CreateConnection  GW1
 SDP data (E1)
2- CreateConnection
(SDP, E1)  GW2
 SDP data (E2)
3- ModifyConnection
(SDP, E2)  GW1
 ACK
E1
GW1
GW2
RTP
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E2
SGCP: connection removal
1- DeleteConnection  GW1
 ACK
Call
agent
E1
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2- DeleteConnection  GW2
 ACK
GW1
GW2
RTP
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E2
State of the art, residential GW
GW
What protocol ?
• H.323 ? (v1, v2, …)
• SIP ?
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Page 7
SGCP architecture (RGW)
The intelligence is centralized in a call
agent, not in the trunking gateway (TGW) or
in the residential gateway (RGW)
SS7/ISUP
STP
Call
agent
SGCP/UDP
IP Network
CO
TGW
RGW
RTP
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Page 8
SGCP: event notification
1- NotificationRequest (ring, off hook?)  GW1
 ACK
2- Notify (off hook!)  Call Agent
 ACK
Call
agent
E1
GW1
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Incoming Call (from PSTN)
Call
Agent
SCP
STP
SS7
Gateway
IP Network
CO
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GT1
GT2
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Page 10
SGCP architecture (H.323)
The call agent implements multiple
protocols, such as SS7 or H.323, uses
SGCP to control the gateways
SS7/ISUP
Call
agent
H.323
STP
SGCP/UDP
RTP
IP Network
CO
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TGW
RGW
May 1998
Page 11
SGCP architecture (SIP)
The call agent can easily implement multiple
protocols. Relaying to SIP is easy, because
SGCP incorporates the SDP protocol.
SS7/ISUP
Call
agent
SIP
STP
SGCP/UDP
RTP
IP Network
CO
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TGW
RGW
May 1998
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SGCP architecture (NAS)
The call agent receives a call to 1-800-INTERNET.
It uses SGCP to parametrize the gateway.
Call
agent
SS7/ISUP
Radius
STP
SGCP/UDP
IP Network
CO
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TGW
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server
SGCP Pros and Cons
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SGCP Pros
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SGCP is based on a Centralized Call
Intelligence Architecture
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Centralized call intelligence can still rely
on distributed systems to achieve high
performance and reliability at an
affordable price.
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SGCP Pros (Centralized Call
Intelligence Architecture)
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Simple and stateless endpoints more reliable
than complex and stateful.
Call Agents with call intelligence and
complexity under physical control by service
provider.
Large number of endpoints not a major OA&M
concern.
Services available strictly a function of Call
Agents:
- Different endpoint vendors not a concern
- Different endpoint software version and
vendor not a concern.
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SGCP Pros (Centralized Call
Intelligence Architecture)
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A must for reliable billing.
Feature change and software updates only
needed on limited number of tightly controlled
and centralized Call Agents.
Total cost of ownership under control.
Higher reliability and better service.
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SGCP Pros

UDP based instead of TCP:
- Support for failover
- Scalable
- Real-time
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No connection setup delay
Avoid TCP retransmission strategy
Small set of simple transactions:
- Low CPU and memory requirement for
endpoint
No need for expensive and resource-hungry
parsers.
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SGCP Pros
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Truly Interoperable endpoints can be
developed cheaply.
Simple to use and program
Powerful enough to support/enable current:
- Basic telephony services.
- Enhanced telephony services, e.g. call
waiting, call transfer, conferencing, etc.
Flexible enough to support future IP telephony
services.
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SGCP Cons
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Centralized Call Intelligence is critical to
system - if Call Agents are unavailable, service
will be unavailable (but servers can be made
highly robust, SGCP supports failover).
Requires low-delay and low-loss network for
optimal performance (but so does VoIP in
general).
SGCP is not yet widely deployed.
No self-announcement, self-provisioning
(could be added, probably outside of SGCP -SGCP uses DNS names, appliance may well
use DHCP).
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SGCP Industry Support
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Standardization
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SGCP is a completely open protocol.
Bellcore will provide a reference
implementation.
SGCP Web site:
http://sgcp.bellcore.com/
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SGCP spec. publicly available at:
http://www.ietf.org/internetdrafts/draft-huitema-sgcp-v100.txt
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SGCP reflector - subscription
[email protected]
May 1998
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Standards Bodies et. al.
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CableLabs
First presentation of SGCP - May 13, 1998
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IETF
Submitted as Internet Draft - May 15, 1998
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ETSI TIPHON
Submitted for Helsinki meeting - May 26,
1998
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IMTC VoIP Forum
SGCP to be presented in mid-July
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Industry Support
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SGCP actively supported and currently being
implemented by Cisco Systems and Bellcore.
Currently working with a cable TV company on
an end-to-end SGCP based Voice over IP
solution.
Several Voice over IP vendors have admitted
privately to be working with “something like
SGCP”
Initial feedback from the industry has been
mostly positive.
Many VoIP vendors already subscribe to the
SGCP reflector to ensure an open and
comprehensive protocol.
May 1998
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